Re: Double sided printing with 3520 all in one printer:

The difference in Top/Bottom margins (when printing portrait orientation) with duplexer feature is something required by the hardware of the unit. When you print single side documents, the printer will feed out the page after printing and the printable area is the widest possible. When you use the duplex feature, the printer prints the first side, but must retain the sheet to feed it in again and turn it upside down to print in the other side. Therefore, the printable area is reduced.

Hope it explains clearly how it works. There's actually nothing you can do to avoid it.

Cheers!

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